While it's not the earliest American patent for a brace or bitstock,
patent #9209 by Erasmus Smith of Norwich, Chenango County, N.Y. makes
a novel attempt to refine the attachment method of bits. Prior systems
had used springs or friction to hold the drilling or boring device
in the chuck. One generally had to file a special notch into each
bit. This meant that every brace had its own set of drill bits that
were not interchangeable with any other brace or holder. Smiths new
approach claimed to eliminate any wear or sloppiness that could develop
over usage with previous systems. There was also an implication that
the changing of tools would be easier and faster.

The actual mechanism claimed in the patent was an eccentric lever that would be pressed against the side of the bit, firmly locking it into position in the receiver socket. This lever would then be further restrained by a spring detent.

It should be noted that for the majority of over 500 patents issued in America for improvement in braces and bitstocks, the method of construction was all metal with wooden handles, in contrast with the type of brace construction in the rest of the industrialized world at that time.